U.S. Pat. No. 3,820,481 discloses a sewing system for the production of pocket inserts, which also permits the working of parts of sewing material in the form of flaps or strips. The quality of such pocket inserts is dependent to a large extent on how the length and shape of such sewing-material parts and pocket insert are adapted to each other.
In order to obtain exact agreement of the lengths of the workpieces, the sewing system is provided with a sensor device which detects the leading and trailing edges of the sewing-material part via a photocell in order to enable a control device to guide the formation of the seams and to cut properly. For this purpose, the control device automatically positions the corner knives in order to make the corner cuts in a manner corresponding to the detected length of the sewing-material part. With respect to the shape of the sewing-material part, a manual entry must be made into the control device, which accordingly controls the functions involved in producing a seam, making the middle cut, and angularly positioning the corner knives which make the corner cuts.
Because of the requirement that there be a manual entry with respect to the shape of the pocket insert to be produced, erroneous entries into the control can impair the quality or even cause rejection of the finished product.
Another difficulty is caused by manufacturing tolerances with respect to the angles with which the sewing-material parts to be sewed together are prepared. As a result, it is frequently necessary for an entry to be corrected. Furthermore, different shapes cannot be worked in rapid sequence.
In view of the necessary inputs, and possibly their correction, as well as verification and monitoring tasks, there is additional work for the operator, as a result of which, in the final analysis, the quality of the product and the output of the sewing system are impaired.
All prior art materials mentioned herein are expressly incorporated by reference.